How would that conclusion change your perception of the Earth, the universe and mankind? Would you still believe all of these were accidental? Would our uniqueness upset your belief in scientific certainty?
Or would you never accept the possibility that we might be alone?
First, any such conclusion would be quite foolish. The vastness of the universe together with the huge number of habitable planets, moons, and whatever that possibly could sustain life is such that no one can know one way or the other. Is it possible that we are alone? Yeah, but the idea that just because we haven't found any life forms elsewhere yet has to mean none exists is to my mind ridiculous.
If we consider the possibility that we are alone is true, would that change my perception of the Earth, the Universe, and Mankind? Nope, don't see why it should. Now, if the Klingons show up tomorrow, then I reserve the right to change my mind.
Would you still believe all of these were accidental? Still? Kinda jumped the shark there a little bit, no? Who says it was accidental? Got any evidence one way or the other? No, you don't, nor does anyone else. Is it possible that life on this planet is accidental? Yes. Is it possible that it isn't? Yes. Is it possible to prove it, either way? No. The word accidental implies an unintentional event; i.e., no God. I ain't going down that rabbit hole.
Would our uniqueness upset your belief in scientific certainty? Scientific certainty of what? There are no certainties for life in the universe other than our own. Anyone who concludes that life does not exist elsewhere in the Universe because we haven't found it yet, is in no position to talk about scientific certainty. There was a time not long ago when the scientific community believed that the Universe was contracting, now they think it's expanding. Is there any certainty about it? I don't think so, and I don't think there are many scientists who are all that certain about life elsewhere either. I believe the prevailing opinion at present is that the sheer number of places where life could sprout is so large that it is almost unbelievable that it hasn't.